Tracing the Second Law

Abstract

This article reviews the evolution in the field of thermodynamics. In the 19th century, James Joule, an English physicist, discovered the equivalence of heat and work, and the First Law of Thermodynamics was firmly established. The Second Law developed in phases over some 125 years. It is one of the most abstract laws of physical science and is the bane of students and others who try to understand its complexity. The first phase in the evolution of the Second Law is older than Joule's work and is due to Sadi Carnot. Carnot published his results in a book, Reflections on the Motive Power of Fire, in 1824. The second phase in the evolution of the Second Law took place in 1849, when William Thomson studied Carnot's work. The third phase of the evolution of the Second Law was carried out by a German professor of mathematical physics, Rudolf Clausius, who became aware of the work of Carnot, Joule, and Kelvin in 1850. A fourth phase in the development of the Second Law was carried out by Lars Onsager in 1931. The fifth phase in the evolution of the Second Law was developed by Ilya Prigogine in 1945. The Second Law is a statement that the entropy content of a system may be increased or decreased by entropy exchanges with the environment, but may only be increased as irreversibilities cause entropy creation.